In the fabrication of integrated circuits and other electronic devices, multiple layers of conducting, semiconducting, and dielectric materials are deposited onto or removed from a substrate surface. Thin layers of conducting, semiconducting, and dielectric materials may be deposited onto the substrate surface by a number of deposition techniques. Deposition techniques common in modem microelectronics processing include physical vapor deposition (PVD), also known as sputtering, chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), and electrochemical plating (ECP).
As layers of materials are sequentially deposited onto and removed from the substrate, the uppermost surface of the substrate may become non-planar and require planarization. Planarizing a surface, or “polishing” a surface, is a process where material is removed from the surface of the substrate to form a generally even, planar surface. Planarization is useful in removing undesired surface topography and surface defects, such as rough surfaces, agglomerated materials, crystal lattice damage, scratches, and contaminated layers or materials. Planarization is also useful in forming features on a substrate by removing excess deposited material used to fill the features and to provide an even surface for subsequent levels of metallization and processing.
Chemical-mechanical planarization, or chemical-mechanical polishing (CMP), is a common technique used to planarize substrates. CMP utilizes a chemical composition, typically a slurry or other fluid medium, for selective removal of material from the substrate. In conventional CMP techniques, a substrate carrier or polishing head is mounted on a carrier assembly and positioned in contact with a polishing pad in a CMP apparatus. The carrier assembly provides a controllable pressure to the substrate, urging the substrate against the polishing pad. The pad is moved relative to the substrate by an external driving force. The relative movement of the pad and substrate serves to abrade the surface of the substrate to remove a portion of the material from the substrate surface, thereby polishing the substrate. The polishing of the substrate by the relative movement of the pad and the substrate typically is further aided by the chemical activity of the polishing composition and/or the mechanical activity of an abrasive suspended in the polishing composition.
As the demand for ever smaller storage devices capable of storing ever larger amounts of information increases, electronics manufacturers have begun to manufacture increasingly complicated integrated circuits utilizing exotic materials. For example, the use of noble metals in DRAMs (dynamic random access memory) and FeRAMs (ferroelectric random access memory) is becoming increasingly popular. While the use of noble metals can provide increased performance in such devices, the use of noble metals can—and often does—present unique manufacturing challenges. In particular, noble metals are mechanically hard and chemically resistant. Indeed, the term noble metal was adopted to describe the metals' superior resistance to corrosion and oxidation. This mechanical hardness and relative chemical resistance make noble metals much more difficult to efficiently polish using conventional chemical-mechanical polishing compositions and techniques.
Notwithstanding the difficulties presented by the chemical-mechanical polishing of noble metals, their potential benefits have driven their use in the manufacture of integrated circuits, and several attempts have been made to develop chemical-mechanical polishing compositions and techniques aimed at aiding their integration into integrated circuit manufacture and the realization of the full potential that can result from their use. For example, U.S. Pat. No. 5,691,219 discloses a polishing composition comprising a halo-compound that is purportedly useful in the polishing of noble metals. Similarly, U.S. Pat. No. 6,290,736 discloses a chemically active polishing composition for noble metals comprising an abrasive and a halogen in basic aqueous solution. WO 01/44396 A1 discloses a polishing composition for noble metals comprising sulfur-containing compounds, abrasive particles, and water-soluble organic additives which purportedly improve the dispersion of the abrasive particles and enhance metal removal rates and selectivity.
While each of the aforementioned chemical-mechanical polishing compositions might be capable of polishing noble metals more efficiently than conventional chemical-mechanical polishing compositions, the compositions also can produce defects on the surface of the substrate that can negatively impact the performance of any integrated circuit later manufactured from the substrate. Furthermore, the halogen- and sulfur-containing compounds utilized in the aforementioned polishing compositions can be highly toxic (which can complicate the polishing process by requiring specialized handling equipment and/or procedures), expensive to produce, and/or expensive to properly dispose of in accordance with environmental regulations.
A need therefore remains for a chemical-mechanical polishing composition that is capable of polishing noble metal containing substrates more efficiently than conventional chemical-mechanical polishing compositions without the need for using specialized oxidizers or chemical etchants. The invention provides such a chemical-mechanical polishing composition and related method of using the same to polish a substrate. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.